This invention relates to heat exchangers, such as vehicle engine cooling radiators, and to a flow control valves therefore control valve that is integrated into the inlet of a U flow type radiator in a simple and non flow restrictive fashion.
Flow control in vehicle engine cooling radiators has historically consisted of just a passively acting thermostat which, reacting to coolant temperature, blocks flow into the radiator to a greater or lesser degree, by passing the remainder of the flow through an by pass path external to the radiator. When wide open at the highest coolant temperature, all flow goes through the radiator. This standard system does not offer a high degree of control, generally using a thermally expandable wax material. Other systems attempt to add an extra degree of control by deliberately and externally heating the wax material to expand it, generally electrically heating it. There has been a recent trend, at least in published patents, toward active, electronically controlled flow control valves. An example may be seen in U.S. Pat. No. 6,314,920. The system shown there requires an electronically controlled coolant pump, and the valve is also external to the radiator, requiring an external by pass circuit around the radiator.
Other patents show control valves internal to the header tanks of the radiator, either passively or actively operated. One example is U.S. Pat. No. 5,305,826 shows a plunger operated double valve, either actively or passively controlled, that simultaneously blocks or opens both the inlet into a radiator of the two pass type, as well as blocking or opening a by pass passage between the two passes. As disclosed, the valve, being just downstream of the inlet, would represent a severe flow restriction within the header tank, in addition to the pressure drop that inherently happens as flow enters a header tank inlet and makes a ninety degree turn. Likewise, U.S. Pat. No. 4,432,410 shows a passively acting by pass valve located within the header tank, just downstream of the inlet. This, also, would represent a significant additional flow restriction and pressure drop. Coolant flow induced pressure drop through the inlet, outlet and header tank of a radiator is a serious issue, and features that add significantly to it are not preferred, despite the desirability of having an internal flow control valve, as opposed to an external flow control valve.
The invention provides an actively controllable radiator flow control valve that is internal to the radiator header tank, but which is integrated therewith in such a way as to not add a large pressure drop.
In the embodiment disclosed, the radiator is a U flow design, with two rows of flow tubes, in which one header tank is split between inlet and outlet portions by a dividing wall, with the inlet on one side and the outlet/pump inlet on the other side. The other header tank would act only to return the flow from the inlet to outlet portion of the first header tank. The physical coolant inlet to the first header tank is a cylindrical barrel that extends not only outside of the tank, as a conventional inlet fitting would, but also through the dividing wall and across the whole width of the interior of the tank. The exterior, outer end of the barrel provides the coolant inlet to the tank, while the inner surface provides a stationary outer housing and guide for the movable inner member of the control valve. Windows in the barrel allow open into the inlet and outlet side of the first header tank, one on either side of the dividing wall. The movable portion of the valve is a hollow cylindrical sleeve, closely and rotatably mounted within the outer barrel. One end of the sleeve opposite the inlet end of the outer barrel, can be turned back and forth about its central axis by a motor or similar actuator. Cut outs in the inner sleeve register with the windows in outer barrel, either completely or partially, or not at all, depending on the relative turned position of the inner sleeve.
Coolant flow entering the exterior end of the outer barrel then flows inside the close fitting inner sleeve, essentially just as it would with a conventional radiator tank inlet, and with no significant additional pressure loss. Depending on the relative registration of the inner sleeve and outer barrel cut outs and widows, flow exits the inner sleeve, and flows into either just the outlet side of the header tank, for a complete by pass of the radiator, or just the inlet side of header tank, forcing all flow through the radiator, or a mixed flow. Mixed flow can constitute the normal radiator operation, as determined by sensed engine or coolant temperature and consequent cooling demand, rather than the conventional operation of total flow through the radiator at all times other than initial warm up. This is feasible since a U flow radiator is inherently more efficient and the valve adds little additional pressure drop. Operating the radiator normally with some degree of by pass saves pump work and energy, regardless of how the pump is driven. Total radiator flow can then be reserved for severe engine cooling requirements.